1. Field of the Invention
The present invention relates to an image signal processing device for recording a color still image on a recording medium or reproducing the same in accordance with a JPEG algorithm.
2. Description of the Related Art
A standardized algorithm for the encoding of high resolution images and the transfer of that information through telecommunication transmission channels has been recommended by the JPEG (Joint Photographic Expert Group). A color still image handled in the algorithm recommended by the JPEG, that is, the JPEG algorithm, can be constituted by a plurality of components, but for example, three components are enough when using a color still image comprised of luminance signals Y and differential color signals Cr and Cb. The other components are not used.
On the other hand, in the baseline process of the JPEG algorithm, to enable large-scale data compression, first the original image data is broken down into components on the spatial frequency axis by two-dimensional DCT transformation, the data expressed on the spatial frequency axis is quantized, and the quantized data is encoded. Accordingly, part of the information of the original image is lost by the two-dimensional DCT transformation and data compression by the quantization, so complete restoration of the original data at the receiving side is not possible.